Methods to improve rigidity of vertically oriented drawer slides

ABSTRACT

Methods include direct and indirect communication of a lifting force to the middle slide of each drawer slide that counteracts the effects of gravity and maintains the maximum elevated position of the middle slide, where said methods cooperating with over-length drawer slides enable further improvement in rigidity.

This application claims priority to U.S. 62/231,362

BACKGROUND

Work surfaces exist for a great many purposes, and it appears a common characteristic that is important and valued is how stable it is. A work surface that wiggles or wobbles is not suitable for many tasks. Preventing this condition in a variable height work surface that is elevated 18 or 21 inches is regarded as very important to persuading customers that it will meet their needs.

In 2014, medical researchers published findings that excessive sitting is significantly detrimental to one's health. This news has boosted new product offerings, and none offer these drawer slide mechanisms. Weakness in the stability of these drawer slides in a variable height work surface application or any vertical application may be the reason.

This weakness is the middle slide assembly including the arrays of ball bearings that is susceptible to gravity in a vertical orientation. After a bit of use, normal human interactions while in an elevated position communicate lateral and torsional forces to the extended slides, relieving the lateral tension of the guide rails on the ball bearings long enough for the middle slide assembly to continue slipping down from the not fully elevated position it may have attained during lifting. A worst case condition also occurs, where from the sitting or starting position, the inner slide extends by itself half of the total travel distance, or phase 1 of the travel before engaging and lifting the middle slide assembly for the remaining phase 2 distance. This minimizes the drawer slide's resistance to lateral and torsional forces.

SUMMARY

Alternatively, if a sufficient lifting force is communicating with the middle slide it will extend along with the inner slide during phase 1 travel, thereby providing the maximum available support resulting in maximum available rigidity of the drawer slide. From this location the phase 2 extension of the unsupported inner slide is the travel distance remaining, where this maximum available support and rigidity drops to the same low level of support at full travel extension as does the drawer slides without this lifting force.

This support and resulting improvement in rigidity of the drawer slides contributes to the rigidity of the work surface. At nearly all elevations excepting the start and end points, this rigidity is significantly greater than without the lifting force applied.

Further improvement in this rigidity is attained when this lifting force cooperates with over—length drawer slides.

Benefits

This recovery and gain in stiffness is significant and believed to be essential to sustaining the quality feel of a variable height work surface for the long term.

Additional support and rigidity is gained by applying this lifting force to over-length slides that further increases the middle slide extension.

The improved stiffness enables drawer slides to compete in vertically oriented applications where they offer low cost ball bearing movements.

Drawer slides that further comprise the features to enable implementing this method are neither difficult nor costly to produce.

Limitations

Drawer slide bearings are exposed to the elements and intended for indoor use.

Suitable for light and moderate load applications.

Requires heavy duty drawer slides for superior results.

DESCRIPTION OF DRAWINGS

FIG. 1 is a left side view of an extended drawer slide cooperating with a work surface underframe vertical object.

FIG. 2 is a left front isometric partial view of an underframe with a smaller diameter constant force spring applying a lifting force to a middle slide of a drawer slide.

FIG. 3 is a left front isometric partial view of an underframe with a larger diameter constant force spring applying a lifting force to a middle slide of a drawer slide.

FIG. 4 is a right side isometric view of an underframe with a constant force spring cooperating with flexible cable manipulated by a pulley to communicate a lifting force to middle slide of a drawer slide.

DETAILED DESCRIPTION

The widespread popularity of drawer slides has supported manufacturers in many countries, and resulted in high volume low cost production of these ball-bearing linear extension mechanisms. Attempting to use these advantages in vertically oriented applications, particularly an adjustable height work surface application, revealed problems that would need cost effective solutions to enable these drawer slides to provide sufficient stability. This exemplary adjustable height work surface application is the first intended application, and the basis of the research herein, where this method improves the rigidity of a purchased component operating in a vertical orientation.

Different methods of lift assistance including motorized and counterbalanced methods that would cooperate with the underframe to elevate it are not shown.

Referring to FIG. 1 showing the left side of an asymmetric work surface 20 cooperating with an underframe comprising vertical components 12 cooperating with the inner slide components 31 attached thereto with just the left side showing. Human interaction such as side impacts to the work surface at location F1 with the work surface result in lateral and torsional forces applied to these inner slide components or inner slides 31 cooperating arrays of ball bearings 34 to the middle slide component or middle slide 32, further cooperating with ball bearings 35 to the fixed outer slide component or outer slide 33 further cooperating with the stability of the base objects (not shown). The travel extent of the middle slide 32, and inner slide 31 are shown as fully extended. The sitting position or starting level 41 for the drawer slides provides the maximum rigidity. The phase 1 of travel extends from 41 to level 51 representing about half of the length of the slide, and the highest level of the middle slide. Phase 2 is the travel distance showing the unsupported inner slide between levels 51 and 61.

The arrays of ball bearings 34, 35 are retained in cages and frictionally cooperate between slide components and movably cooperate with the movements of the extendable middle and inner slides due to rolling contact of the ball bearings initiated by the movement of one slide in relation to another. This results in vertically extending all of these components in relation to the fixed position of the outer slide 33, and subjecting them to the force of gravity. The inner slide 31 will extend half its length out of the middle slide 32 before features of the inner slide engage features of the middle slide that insures the middle slide is extended and retains its position when the inner slide is fully extended. Lateral loads in this vertical orientation retain the elevated ball bearings and middle slide. The lateral fraction of a downward load in this vertical orientation is relatively low where human interaction can easily reduce or reverse this lateral load. After a bit of use, normal human interactions producing lateral and torsional forces relieve lateral loads on the ball bearings long enough for gravity to urge the middle slide assembly to continue slipping down from a not fully elevated position it may have attained during lifting.

A new slide is manufactured to produce slight interference fits between the slides and the ball bearings providing a slight normal force applied to the ball bearings enabling the relative movements between the slides to cause the arrays of ball bearings to appropriately advance and retain their advanced positions. However, with normal use and exposure to loads and forces, this normal force degrades, enabling gravity to retain the middle slide and ball bearing arrays while the inner slide initially extends from the starting level 41 to level 51 before its features begin extending the middle slide.

Since the loads and forces in this application are initiated at the work surface, and this extended and unsupported half of the inner slide is the least able to communicate loads and forces without distortion, it is described as the providing the minimum stiffness available in this vertical orientation.

A method to improve the available stiffness of the drawer slides in a vertical orientation is described where minor modifications to the leading ends of the inner and middle slides were required. These modifications enable the leading end of the middle slide to further comprise a feature that cooperates with an object that communicates a sufficient lifting force to the middle slide.

The lifting force urges the middle slide to remain in contact with its upper stop, enabling it to extend along with the inner slide during phase 1 travel to level 51, and is retained by the lifting force as the inner slide further extends with the underframe through phase 2 travel to full extension.

Applying this lifting force maximizes the support provided by the middle slide to the inner slide during the phase 1 travel, and maximizes the proximity of this support as the inner slide further extends in phase 2 travel. Although there is no improvement in stiffness at level 41 or level 61 there is significant improvement in stiffness at the elevated positions between these levels.

This method further enables the use of over length slides that never reach full extension. Using an over length drawer slides in cooperation with applying a lifting force to the middle slides increases the extended elevation level 51 of the middle slides and the support provided, while also reducing the phase 2 travel distance of the unsupported inner slide. These advantages increase the travel distance providing maximum support, and further maximize the proximity of this support to the further extended inner slide. The available stiffness is further increased primarily in the second half of elevated travel including the level 61 position.

While features proximate to the leading ends of the inner and middle slides 32 may vary from one manufacturer to the next, a cooperating feature as common as a hole or threaded feature, or other modification has to be added to the middle slide to connect an object providing a lifting force.

The inner slide 31 leading end features may interfere with a preferred connected object and may also require a modification. Providing drawer slides with the one or more added features described, with or without a lifting force object, and intended for the purpose described herein is considered within the scope of this application.

Referring to FIG. 2, a small diameter constant force spring 10 cooperates with a hub rotationally cooperating with a shaft 14 that cooperates with the under frame vertical object 12 in a cutout 11 above the inner slide. The underframe also comprises a panel object 13 cooperating with a second vertical object 12 (not shown), that further cooperates with a second similarly configured drawer slide further cooperating with a second base object.

The free end feature 10 b of each spring cooperates directly or indirectly to the cooperating feature added to the middle slide where a sufficient extended distance of the free end from the spring coil preloads the spring to provide the lifting force. This exemplary view is one of several known arrangements for mounting these springs considered within the scope of this description.

Referring to FIG. 3 a larger diameter constant force spring 10 providing very long life cooperates with a hub rotationally cooperating with a shaft 14 that cooperates with brackets 19 connected to the under frame vertical object 12 above the inner slide. Cutout 11 in vertical object 12 is required. The preload distance is greater for the larger diameter, which limits the use of over-length slides.

Referring to FIG. 4, the underframe vertical component 12 cooperates with a panel object 13 that would further cooperate with a second vertical component 12 further cooperating with a second similarly configured drawer slide cooperating with a second base object.

In this exemplary view, the object connected to the middle slide 32 cooperating feature comprises a cable end fitting 18 connected to a flexible cable 15 that loops over a pulley 16 cooperating with bracket 17 in a cutout of object 12, and into the underframe. The second end of the cable is connected directly or indirectly to the free end 10 a of a constant force spring 10 mounted on a hub rotationally cooperating with shaft 24 cooperating with an underframe panel 13. It is important to add the preload distance and the extended travel distance when locating the spring, and preparing the cable. This configuration enables larger diameter springs to communicate a lifting force to over-length drawer slides.

In the majority of applications, drawer slides are used in pairs, where the opportunity to further manipulate the orientation of a plurality of lifting cables to cooperate together with one or more springs is within the scope of this method of communicating a lifting force to a plurality of middle slides using springs. 

1. A method to improve the rigidity of vertically oriented drawer slides typically implemented in pairs cooperating with a movable object or an underframe of an adjustable height work surface and further cooperating with one or more base structures that enable linearly constrained vertical movement of the object or underframe, wherein:
 1. the leading ends of each middle slide of each drawer slide further cooperates with one or more objects that communicate a lifting force sufficient to lift the middle slide assembly, the one or more objects further cooperating with the underframe,
 2. said one or more objects further capable of extending while continuing to provide a sufficient lifting force throughout the vertical travel range, thereby maximizing the middle slide support of the inner slide, resulting in improved rigidity of the drawer slide for the majority of said travel range,
 2. The method of claim 1 where the one or more objects is a spring or springs with sufficient preload prior to elevating the underframe, and capable of extending the distance of the phase 2 travel.
 3. The method of claim 2 where the one or more spring objects comprise one or more constant force springs mounted on hubs rotationally cooperating with shafts cooperating with the underframe, the free ends of the springs further comprising a preferred feature or object that cooperates with a middle slide feature to communicate the lifting force.
 4. The method of claim 1, where each object connected to each middle slide is a length of flexible material further comprising a connecting object or feature capable of communicating the lifting force, said flexible material further manipulated by one or more: pulleys, hubs, sprockets, cable housings, or guides, to a preferred orientation within or adjacent to the underframe, the second ends of the flexible material cooperating with one or more preloaded springs further cooperating with the underframe, wherein:
 1. the spring or plurality of springs cooperating with the plurality of flexible materials separately or together, provide the lifting force resulting in improved rigidity of the drawer slides.
 5. The method of claim 4 where the one or more springs are constant force springs further cooperating with hubs rotationally cooperating with shafts cooperating with the underframe, the free ends of the springs further comprising a preferred feature or object that cooperates with a flexible material to communicate the lifting force.
 6. The method of claim 4 cooperating with over-length drawer slides provides an extended height of phase 1 elevation of the middle slide, while reducing the remaining phase 2 travel distance of the inner slide, thereby further improving the rigidity of the extended drawer slide.
 7. A drawer slide further comprising one or more features and modifications and identified as enabling customers to easily apply said modified drawer slides in vertical orientations wherein:
 1. a feature is provided proximate to leading end of the middle slide to easily connect an object that communicates a lifting force to the middle slide, enabling the improved rigidity benefits.
 8. The method of claim 6 where a drawer slide further comprises a preferred flexible material or spring object, further enabling customers to easily apply said modified drawer slides in vertical orientations, and enabling the improved rigidity benefits. 